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Table 1 Summary of correction factors applied probabilistically to samples from SFB

From: Risk characterization of microplastics in San Francisco Bay, California

Sampling Apparatus Matrix Mesh Size (μm)a Alpha (unitless; median, 5th to 95th percentiles) CFb (unitless; median, 5th to 95th percentiles) Proportion of Particles Confirmed Plastic (unitless; median, 5th to 95th percentiles; probability distribution) Fiber Correction Factor (unitless; median, 5th to 95th percentiles; probabilty distribution) Combined Correction Factors (unitless; median, 5th to 95th percentiles)
1-L grab Surface water 50 2.07 (2.02 to 2.12)c
2.15 (1.36 to 2.93)d
66 (55 to 80)c
90 (5 to 1988)d
0.40 (0.19 to 0.72)
beta: shape 1 = 6.03,
shape 2 = 137
NAf 26 (12 to 48)c
35 (1.7 to 823)d
24-hr pipe Stormwater 106 2.97 (1.62 to 4.35)d 9361 (20 to 6,120,045)c NAe NAf 9361 (20 to 6,120,045)c
Composite WWTP effluent 110 2.54 (2.52 to 2.56)c
2.41 (2.18 to 2.64)d
1396 (1292 to 1507)
762 (256 to 2290)d
0.27 (0.09 to 0.64)
beta: shape 1 = 3.00,
Shape 2 = 93.5
NAf 384 (119 to 888)c
202 (44 to 825)d
Manta Trawl Surface water 333 2.07 (2.02 to 2.12)c
2.15 (1.36 to 2.93)d
529 (401 to 704)c
797 (12 to 73,349)d
0.72 ± 0.24 (65)
beta: shape 1 = 5.81,
shape 2 = 73.7
9 (1 to 52)
Normal (log10-transformed): mean = 0.965, stdev = 0.529
2819 (336 to 17,966)c
4103 (41 to 554,392)d
Otter trawl/cast net Biotac / fish tissued 25 2.59 (2.52 to 2.66)c
2.26 (1.92 to 2.60)d
167 (135 to 2066)
58 (20 to 1750)d
0.23 (0.09 to 0.46)
beta: shape 1 = 4.20,
shape 1 = 169)
NAf 38 (14 to 80)
13 (3 to 49) d
Van Veen Grab Sediment 45 2.57 (2.24 to 2.90)c
2.90 (2.22 to 3.59)d
394 (113 to 1398)c
1342 (103 to 18,861)d
0.34 (0.16 to 0.69)
log-normal: meanlog = −3.39, sdlog = 0.44
NAf 133 (32 to 553)c
454 (31 to 6860)d
  1. aConcentrations were rescaled to 1 to 5000 μm
  2. bExact mesh size values as reported in Zhu et al. [70] were used to rescale data
  3. cValues from Kooi et al. [37] and derived from various locations in Europe. Alpha values for stormwater have not been reported elsewhere in the literature. Alpha value reported for biota in Kooi et al. [37] are primarily polychaetes
  4. dDerived using site-specific data for San Francisco Bay obtained from Zhu et al. [70]
  5. eStormwater particle-level data were not reported in CEDEN and could not be obtained to perform this analysis
  6. fFibers were only systematically removed from manta trawl samples, so fiber correction factors are not applicable for other sampling apparatuses